Kaolinite suspension as a model fluid for fluid dynamics studies of fluid fine tailings

The rheology of fluid fine tailings is studied and compared with that of kaolinite suspensions having the same zeta potential, solid volume fraction and relatively similar particle size distribution. The suspensions were examined under shear and oscillatory deformation fields to investigate their yielding, aging, and steady-state flow behavior under shear rate and stress-controlled conditions. Using dynamic strain sweep experiments, it is shown that the samples exhibit a maximum in their loss modulus during yielding while they exhibit two different regimes of strain dependency in their fluidized regime. Samples are found to exhibit a plateau region in their stress-strain curves measured by the dynamic strain sweep experiments, due to the presence of flow instabilities. Small amplitude oscillatory tests are performed to study aging behavior of the suspensions with different shear histories. The aging process is found to depend strongly on the shear history of the samples prior to rest. Shear flow experiments under stress-controlled conditions show that both suspensions exhibit a plateau in their flow curves where a slight increase of the shear stress results in a dramatic change of the shear rate, implying the occurrence of shear-banding flow instability. This agrees with the behavior observed in the oscillatory deformation mode and implies that below a critical shear stress, no stable flow can be achieved in the suspensions. Fluid fine tailings and kaolinite suspensions are found to exhibit fairly similar rheological behavior, when their zeta potentials, solid volume fractions, and particle size distributions are matched.